Moderate to severe premenstrual disturbances afflict up to 15-20% of women. After years of treatment research that was notable for inconsistent findings, researchers have identified agents that effectively treat women suffering from these conditions. An appealing treatment modality for ameliorating symptoms in women with premenstrual dysphoric disorder (PMDD) is the use of SRIs only during the luteal phase of the menstrual cycle, an approach supported by several randomized clinical trials. Medication administered in this way limits both drug exposure and side effects to the symptomatic phase of the cycle and is often preferred by patients. Given positive efficacy studies for luteal-phase dosing, it is likely that the Food and Drug Administration will approve the use of this modality for the treatment of moderate to severe premenstrual conditions such as PMDD. Yet, this is a treatment modality that has only been evaluated in controlled clinical trials, and features that may have enhanced positive study results (monitoring ovulation, compliance counseling by vigilant study staff, and direction regarding when to initiate medication) are noticeably absent in routine clinical practice. Furthermore, evidence suggests that patients in clinical trials who were able to comply with luteal-phase dosing are not representative of women commonly seen in clinical practice, and thus the feasibility of luteal-phase dosing is unclear. This is a revised R-21 application that responds to PAR-99-118, "Pilot Effectiveness Trials for Mental Disorders" The specific alms of this application are to: 1) Evaluate whether women In a primary care ob-gyn practice with moderate to severe PMS will be willing and able to adhere to psychotropic medication treatment that is limited to the luteal phase of the menstrual cycle; 2) Determine whether specific patient characteristics (suffering from moderate to severe PMS that does not meet criteria for PMDD versus suffering PMDD; having another co-occurring psychiatric or general medical condition that is not limited to the luteal phase of the cycle versus not having other disorders) influence response to Intermittent SRI treatment; 3) Evaluate whether a retrospective scale administered in conjunction with a psychiatric screening scale can identify women with moderate to severe premenstrual changes; 4) Compare and select outcome measures that are most able to show improvement in premenstrual symptoms after treatment with an SRI; and 5) Collect symptom data on treatment as usual in order to estimate the effect size required for a subsequent study.